It has been proposed in U.S. Pat. No. 3,841,953 to form nonwoven webs of melt-blown fibers using polymer blends, in order to obtain webs having novel properties. A problem with these webs however is that the polymer interfaces causes weaknesses in the individual fibers that causes severe fiber breakage and weak points. The web tensile properties reported in this patent are generally inferior to those of webs made of corresponding single polymer fibers. This web weakness is likely due to weak points in the web from incompatible polymer blends and the extremely short fibers in the web.
A method for producing bicomponent fibers in a melt-blown process is disclosed in U.S. Pat. No. 4,729,371. The polymeric materials are fed from two conduits which meet at a 180 degree angle. The polymer flowstreams then converge and exit via a third conduit at a 90 degree angle to the two feed conduits. The two feedstreams form a layered flowstream in this third conduit, which bilayered flowstream is fed to a row of side-by-side orifices in a melt-blowing die. The bilayered polymer melt streams extruded from the orifices are then formed into microfibers by a high air velocity attenuation or a "melt-blown" process. The product formed is used specifically to form a web useful for molding into a filter material. The process disclosed concerns forming two-layer microfibers. The process also has no ability to produce webs where web properties are adjusted by fine control over the fiber layering arrangements and/or the number of layers. There is also not disclosed a stretchable and preferably high strength web.